1. Field of the Invention
The invention relates to a current collector and a gas circuit breaker, and more particularly, to a current collector, in which moving and fixed contacts constituting a breaker for making an electric circuit ON and OFF come toward and away from each other to thereby carry and shut off current, and a gas circuit breaker.
2. Description of the Related Art
Typical of this type of gas circuit breaker is a puffer type gas circuit breaker. With this type of gas circuit breaker, an interrupting section is arranged in a metallic container filled with an arc-extinguishing gas such as SF6 gas to be insulated electrically from the container, the arc-extinguishing gas is compressed in a compression device in relation to coming toward and away actions of contacts (current collector), which constitute the interrupting section, and the compressed gas is blown against an arc to extinguish.
An explanation will be given to conventional contacts (current collector) constituting an interrupting section of such puffer type gas circuit breaker.
FIGS. 5A, 5B and 6 show each a conventional current collector. In these figures, an outside fixed contact 14 formed from an electrically conductive member and an inside moving contact 13 are constructed to be concentrically cylindrical structure in a fitting contact relationship (the outside fixed contact 14 is cylindrically structured to be hollow and torus-shaped, and the inside moving contact 13 is cylindrically structured to be hollow or solid). Current flows, for example, to the inside moving contact 13 through a contact portion 15a from the outside fixed contact 14. The inside moving contact 13 is constituted so as to move on the outside fixed contact 14 with a circuit opening and closing operation of a circuit breaker so that a current-carrying contact portion slides. Formed on the fixed contact 14 are n slits, which extend therethrough radially, run a predetermined length in an axial direction, and partial fixed contacts 141, 142, - - - 14n constitute the fixed contact 14. Before the moving contact 13 and the fixed contact 14 fit together, the fixed contact 14 has an inside diameter xcfx86D1 and an outside diameter xcfx86D3 while the moving contact 13 has an outside diameter xcfx86D2. Here, by virtue of xcfx86D1 greater than xcfx86D2, when the moving contact 13 and the fixed contact 14 fit together, an outside diameter of the fixed contact 14 becomes xcfx86D3, greater than xcfx86D3 so that the fixed contact 14 is flexed outward to give contact forces to the contact portion 15a. 
However, with the above structure of a conventional current collector, as seen in FIG. 7 showing the detail of the contact portion 15a between the moving contact 13 and the fixed contact 14, inside and outside diameters of the moving contact 13 and the fixed contact 14 have the relationship of xcfx86D1 less than xcfx86D2 and a processing problem is involved, so that the actual contact portion 15a forms the only part of circumferential end portions of the moving contact 13 and the fixed contact 14.
When the moving contact 13 and the fixed contact 14 slide in such contact (current-carrying) state, there is caused a problem that temperature rise is caused locally due to the high current density in the contact portion 15a, so that the members are decreased in hardness whereby the contact portion 15a undergoes excessive dissolved loss as compared with the case where the moving contact 13 and the fixed contact 14 do not slide relative to each other to decrease the durability of the current collector extremely.
The invention has been made in view of the above point, and has its object to provide a current collector or a gas circuit breaker, which is enhanced in durability as well as current-carrying performance without causing dissolved loss in a contact portion even when both moving and fixed contacts come into sliding contact with each other.
In order to attain the above object, the invention provides a current collector comprising a container, with an insulating arc-extinguishing medium being sealed therein, has a cylindrical-shaped fixed contact and an torus-shaped moving contact disposed concentrically with the fixed contact and adapted to come into fitting contact with the fixed contact to carry current stored therein, and a torus-shaped current collecting member formed from a conductive material is provided on a contact portion of either of the fixed contact and moving contact.
In order to attain the above object, the invention also provides a gas circuit breaker comprising a container with an insulating gas sealed therein, a fixed contact arranged in the container, a moving contact disposed facing the fixed contact in an opposed manner to be able to come toward and away from the fixed contact, a central shaft having a hollow portion and for making the moving contact movable by an operating force transmitted via an insulating rod from an operating device, a compression device provided outside of the central shaft for compressing a gas blown against an arc generated between the fixed contact and the moving contact, and an insulating nozzle for conducting to the arc the gas compressed by the compression device, wherein the fixed contact and the moving contact are connected together via a torus-shaped current collecting member to permit current to be carried.